852 



SCIENCE. 



[X. S. Vol. XXI. Xo. 544. 



A detinite procedure is followed in the 

 setting and care of protozoan cnltnres with 

 a medium of hay infusion. The seed here 

 used came from previous laboratory cul- 

 tures or from field collections. The physio- 

 logical conditions are determined at almost 

 daily intervals by physical and chemical 

 methods. Evidence so obtained points to 

 fermentative action as the beginning of 

 metabolism in the culture. The curve for 

 acidity is of much physiological signifi- 

 cance. An approximate method of estima- 

 tion is used to compare the relative abun- 

 dance of the different organisms and the 

 results are represented by curves. Rela- 

 tive curves have been approximately deter- 

 mined for bacteria, Golpidiuni, Paramoe- 

 cium, Amoeba, some Hypotricha, Arcella, 

 some Rotifera and Stentor. All efforts to 

 change well-defined curves to decidedly 

 different relative positions in the history 

 of the culture have failed. The maxima 

 of the curves can not be interchanged by 

 teseeding. Since reseeding was not prac- 

 tised (except for experiment) the cysts or 

 spores of all the organisms found must have 

 been continually present. Mutual antag- 

 onism of the different forms is -not a prob- 

 able explanation. The serial succession of 

 the organisms and the parallel physico- 

 chemical changes in the environment point 

 to specific adjustment as a probable hy- 

 pothesis. The determination of some of 

 the specific adjustments of Paramoecium 

 and Htentor supports this hypothesis. 



An Analysis of Physiological Conditions in 

 a Protozoan Cidture: Amos W. Peters, 

 Zoological Laboratory, University of 

 Illinois. 



The influence of the physiological states 

 of protozoa in producing variations from 

 a supposed standard is seen in the results 

 of experiments upon both the directional 

 and the metabolic reactions of this group. 

 To obviate this important difficulty the 



writer proposes to standardize the given 

 conditions of any culture. Standardiza- 

 tion of the conditions, if successful, uses the 

 peculiarities of the physiological states for 

 a more accurate interpretation of the re- 

 sults of experiment, instead of leaving these 

 states as objectionable factors in an experi- 

 mental procedure. 



The methods to be used must conform to 

 at least two conditions. First, they must 

 not require more than a small amount of 

 culture liquid (5 to 10 c.c.) for a test, in 

 order that serial observations can be 

 made upon the same culture. Second, they 

 must be sufficiently accurate and sensitive 

 to yield results that show the successive 

 small differences which occur in the history 

 of a single culture. The special methods 

 here applied are mostly volumetric and 

 comprise the determination of: (1) Quali- 

 tative chemical content, (2) free acidity or 

 alkalinity, (3) dissolved oxygen, (4) bi- 

 carbonates, (5) alkali earths, (6) electrical 

 conductivity, (7) oxygen consumed, (8) 

 sulphated nitrogen, (9) ammoniaeal nitro- 

 gen, (10) individual salts — nitrites, ni- 

 trates, chlorides, potassium, calcium, etc. 

 For both convenience and accuracy, a sys- 

 tem of standardizing all the necessary 

 volumetric solutions in terms of one orig- 

 inal standard acid has been devised. By 

 these methods one series of data has been 

 taken from various media promiscuously 

 selected for comparison, and another series 

 comes from the history of single cultures. 

 In both series the biological aspect of the 

 media was known. Comparison of the 

 physicochemical and the biological data in- 

 dicates that variations in the former are 

 an approximate expression for correspond- 

 ing changes in the physiological states of 

 the organisms. The methods here selected 

 are therefore serviceable for the physio- 

 logical estimation of the protozoan environ- 

 ment. 



